A weak layer of surface hoar has produced very large avalanches in recent days at treeline and below. Stick to low angle terrain and exercise a high degree of caution around open glades and leeward terrain features.
Storm snow is most likely to show slab properties where it has been deposited into wind slabs in lee terrain features. Wind slabs are most reactive during their formation.
In wind sheltered areas, low density storm snow may be prone to sluffing especially with skier traffic.
50-80 cm of snow sits on a persistent weak layer that was buried near the end of January. This layer consists of a melt-freeze crust in some areas, surface hoar in sheltered areas, and facets in some areas. This layer has been the most reactive at treeline and below treeline, where it exists as surface hoar.
Another layer of surface hoar that was buried in mid-January may still be possible to trigger, and it is now down about 80-100 cm.
Friday night: Partly cloudy, moderate to strong northwest ridgetop wind, alpine temperature -6, freezing level valley bottom.
Saturday: Patchy snowfall with target areas receiving 10-15 cm, moderate westerly ridgetop wind, alpine high -7, freezing level 800 m.
Sunday: Mix of sun and cloud, light northwest ridgetop wind, alpine high -12, freezing level valley bottom.
Monday: Mix of sun and cloud, light northwest ridgetop wind, alpine high -13, freezing level valley bottom.
There have been numerous large natural, human and explosive triggered avalanches reported over the last couple of days. These include size 2-3 results from explosive work conducted Friday at Kootenay Pass as well as multiple size 2-3 avalanches remotely triggered by skiers on Thursday. Most of these avalanches failed on the recently buried persistent weak layer. Many occurred at elevations around treeline where the layer exists as surface hoar.
It is notable that a size 3.5 was reported to have failed on a crust that was buried in early December. A smaller avalanche stepped down to this deeper layer, resulting in a very large and destructive avalanche.
Localized snowfall may bring 10-15 cm of new snow to some areas over the day Saturday. This new snow falls on top of quite a complex snowpack.
30-60 cm of recent snow may sit on a weak layer which exists as a freezing rain crust in some areas and surface hoar in others.. It is not known how widespread this layer is, but it may have the potential to produce avalanches where it exists.
There is now about 50-80 cm of recent snow sitting above a widespread persistent weak layer that consists of facets in some areas, a melt-freeze crust in many areas, on a sun crust on steep south-facing slopes, and large surface hoar in sheltered areas. This layer has been the most reactive at treeline and below treeline, where it exists as surface hoar.
There are potentially several more layers of surface hoar in the upper snowpack, with the most notable one down about 80-120 cm. This layer was buried in early January.
A crust surrounded by weak faceted grains is buried deep within the snowpack. It may be possible to trigger this layers with a large load.
